Ecology and biogeography of Cassia brewsteri: assessment of potential sites for cultivation

Abstract

Cassia brewsteri (F. Muell.) F. Muell. ex Benth. has been identified as a potential multipurpose agroforestry species, and also as a potential source of seed galactomannans (industrial gums). In this study, the natural and cultivated distributions of C. brewsteri were used as a basis for predicting potential sites for cultivation of the tree, using the climate modelling software ANUCLIM. The natural distribution was determined by compilation of data from herbaria and from field studies. The ecological parameters of natural occurrences were characterised in terms of soil and vegetation types by sampling 113 sites throughout the natural distribution in Queensland (18.583–26.150°S, 144.750–152.750°N). In addition to the natural occurrences, a further 11 sites were identified where the tree has been grown successfully in cultivation. Failures of the tree in agroforestry trials in Thailand may be explained by high temperature as a limiting factor in the distribution of the species. Failures of the species in trials in Australia, Zimbabwe and Malawi could not be attributed to climate or soil conditions at the trial sites, indicating that further research on culture of the tree is required to achieve high survival and growth rates.